Scientists have no tool for studying UV light after the Hubble retires

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If NASA stands firm on its decision to let the Hubble Space Telescope die in about 2007, scientists will lose among other things their only tool for studying ultraviolet (UV) light coming from all corners of the cosmos. To fill the need, astronomers around the world are advocating the construction of a World Space Observatory they say could launch by 2009.

UV light is absorbed in Earth's atmosphere and so must be studied from space.

The proposed new observatory would not only be more capable than Hubble in the UV arena but would represent a whole new approach to big-time astronomy. The effort involves countries large and small trying to cobble together enough money to build the first truly global space telescope.

In constructing and flying Hubble, NASA cooperated with the European Space Agency. But NASA calls the shots and has sole control over whether Hubble will be serviced, extending its life for several more years. If the servicing is not done, Hubble's batteries and guiding gyroscopes are unlikely to last more than 2-4 more years.

Plans for a final piloted servicing mission to Hubble, which would also have added two new instruments, were cancelled in January by Sean O'Keefe, NASA's administrator, in a decision criticized by many astronomers as not involving the wider scientific community. O'Keefe cited astronaut safety concerns that could not be adequately addressed with reasonable resources.

NASA's decision has only added urgency to the World Space Observatory (WSO) project.

Global interest
The WSO is tentatively supported by 14 countries, with others interested in signing on, proponents say. The United States is not among the participants.

If launched, the telescope would involve an unprecedented cooperative effort extending to countries rarely noted for their space or astronomy programs. The observatory's "implementation committee" has representatives from 19 nations, including Germany, France, Italy, China, and smaller countries like Sweden, Norway, the Ukraine and the Baltic states. The United Nations is also participating, as is the multinational European Space Agency (ESA) on a limited advisory basis.

The Russian Federal Space Agency recently took leadership of the project.

"The World Space Observatory is a completely new approach to carrying out space science, spreading the overall costs across a much larger number of countries than in the past," says Martin Barstow of the University of Leicester in the UK. "At the moment, it is the only potential replacement for Hubble in the ultraviolet and it is essential that the worldwide community supports the project."

Barstow presented his case last week at a meeting of the Royal Astronomical Society.

The WSO would not make visible-light or infrared images, as Hubble does. NASA's replacement for Hubble, the James Webb Space Telescope, will launch no sooner than 2011 and capture only infrared light.

Visible-light astronomy can be done from the ground, though telescopes struggle to consistently match Hubble's performance. Ultraviolet astronomy can't be done from the ground, so Barstow and others are keeping their focus on the loss of UV capability.

"When Hubble finally fails, access to one of the most important parts of the spectrum will end for the foreseeable future," Barstow says.

UV value
Isabella Pagano, of the Osservatorio Astrofisico di Catania in Italy, told SPACE.com that NASA's decision to not service Hubble adds urgency to the WSO project. She said UV light "carries a wealth of information precious in every field of modern astrophysics, from solar system objects to stars, star forming regions, interstellar medium, supernovas, galaxies," and more.

Ultraviolet light is just outside the visible range, toward the higher-energy side of the electromagnetic spectrum. The highest-energy light is in the form of X-rays and gamma rays. Visible light is in the middle, with infrared light, microwaves and then finally radio waves on the lower end.

Astronomers need to study many objects in multiple bands of the overall spectrum to get a complete picture of its activity and composition.

Construction on the WSO has not begun and funding is not secured, so its future is uncertain. In fact, the funding challenge will be as unorthodox and multi-pronged as the many member nations implies. Proposals have been submitted to funding agencies at several of the countries involved.

"We are trying to do this project without a major agency lead -- that is from NASA or ESA," Pagano said, "although we will look for technical support from them to ensure the project is managed in an appropriately rigorous way to ensure technical success. The intention is to share the cost across many more countries than is usual and, in particular, also involve emerging nations with varying levels of space experience to stimulate their science bases."

There is optimism among proponents that the project will be funded and that it could launch within five years. One key to such a short time frame is a conservative plan that calls for using existing or modified technologies in constructing the telescope.

"Therefore a time scale of about five years from now until launch seems to be realistic," said Norbert Kappelmann of Tuebingen University in Germany. "The funding is at the moment the crucial point to aim for a launch in 2008/2009."

For now, the various countries and institutions involved are spending relatively small sums to study the instruments or expertise each would contribute to the project. Kappelmann said a status report of the overall mission is due out by the end of the year.

Potential boon
The WSO would be a boon to UV astronomers. Because Hubble multitasks across infrared, visible and UV, only about one-third of its time is allocated for UV observations with, Kappelmann said, 10 times more requests for observing time being submitted than are accepted.

Not only would WSO be UV-only, it would be five to 10 times more sensitive than Hubble, Kappelmann said.

"Certainly, a decent UV space telescope, perhaps the WSO, is needed after the Hubble Space Telescope" stops working, said Bengt Edvardsson, an astronomer at Uppsala University in Sweden who had not heard of the project until recently.

Karel van der Hucht, senior research scientist at Space Research Organization Netherlands in Utrecht, is particularly worried that a gap of some years in UV capability could force scientists and engineers to move on to other fields.

"Without servicing the Hubble Space Telescope, no UV observational capabilities would be available to the scientific community at all," van der Hucht said via e-mail. "One of the dangers on the horizon is that a new generation of astronomers might be created where all the expertise which has been built up during the times of the previous UV missions might be lost and would be very difficult to recover."

Van der Hucht also cites a somewhat less tangible benefit of the WSO: The ability of scientists in countries not normally involved in space activities to get data from the WSO project "would be extremely beneficial."